(1) Field of the Invention
The present invention generally relates to a communication apparatus capable of data communications and speech communications using a telephone set, and more particularly to a communication apparatus selectively performing a reception procedure in a data communication or a process for outputting a ringing tone to call an operator in a speech communication in accordance with a received signal.
(2) Description of the Related Art
A facsimile machine which can selectively perform a facsimile communication which is a type of the data communications or a speech communication has been proposed. In this type of facsimile machine, the facsimile machine determines whether the communication required by a calling station is the facsimile communication or the speech communication in accordance with received signals. When the speech communication is required by the calling station, the facsimile machine outputs a ringing tone so as to call an operator. When the facsimile communication is required by the calling station, the facsimile carries out an automatic receiving process in the facsimile communication. In this type of facsimile machine, when the operator called by the ringing tone performs predetermined operations including an off-hook operation of the telephone set, the speech communication to the calling station can be carried out via the telephone set.
In the facsimile disclosed in Japanese Patent Laid Open Publication No. 62-260473, the type of communication required by the calling station is determined in the following manner.
After a called facsimile is connected with a line, a received signal is monitored for a predetermined time. When a calling tone signal (a CNG signal) is detected while monitoring the received signal, the reception procedure in the facsimile communication starts. On the other hand, when the CNG signal is not detected, the operator is called by a buzzer or the like.
The CNG signal is a signal transmitted first from the calling station in an automatic calling mode. However, a timing at which the CNG signal is transmitted varies in accordance with the type of calling facsimile machine. For example, one facsimile machine outputs the CNG signal immediately after a called facsimile is connected with the line. Another type of facsimile outputs the CNG signal a predetermined time, such as 10 seconds, after the called facsimile is connected with the line. Thus, the time required for monitoring the received signal must be long to always accurately detect the CNG signals transmitted from the various types of calling facsimiles.
When the speech communication is required by the calling station, a telephone set of the calling station is maintained in a silent state until the called operator responds to the call by using the telephone set. Thus, in the case where the time required for monitoring the received signal is long, the telephone set of the calling station is maintained in a silent state for a long time. In this case, a calling operator feels uneasy.
Conventionally, a facsimile machine disclosed in Japanese Patent Laid Open Publication No.2-7763 has been also proposed. In this type of facsimile machine, when the buzzer starts to be activated to call the operator after it is determined that the speech communication is required by the calling station, a predetermined signal tone is transmitted to the calling station.
However, as the telephone set of the calling station is maintained in the silent state until the conventional facsimile detects that the speech communication is required by the calling station, if the time for monitoring the received signal is made long in order to accurately detect the CNG signal, the telephone set is maintained in the silent state for a long time. Thus, in this case also, the calling operator feel uneasy.